The present invention relates to a data switching system, and, in particular, relates to such a system which is suitable for handling a call of a facsimile terminal which transmits a large amount of information in only one direction.
Two of the prior data switching systems are a circuit switching system and a packet switching system. Those two systems are separately utilized according to the quantity of the information to be transmitted, the cost of the switching system, and the cost of the transmission line. That is to say, a circuit switching system establishes a connection between a calling terminal and a called terminal at the beginning of the communication, and performs no call processing during the communication. Therefore, circuit switching system is suitable for a call which transmits a large amount of data. On the other hand, a packet switching system transmits information by packing data in a packet, and shares a transmission line with other calls. Therefore, a packet switching system is suitable for the terminal which transmits a small amount of data.
It should be noted that in a facsimile communication system for transmitting picture information, a large amount of data is transmitted from the sending terminal to the receiving terminal but the data to be transmitted in the backward direction (from the receiver to the sender) is rather small. Therefore, when a circuit switching system is used for facsimile communication there exists little chance for the backward channel to utilize its ability. When a packet switching system is used for facsimile communication the load of the exchange is sometimes too heavy for handling a large amount of picture data.